1. Technical Field
This disclosure generally relates to nut plate assemblies and methods of using the same.
2. Description of the Related Art
Rivetless nut plates are often installed into structural workpieces in order to couple components to the workpieces. Conventional nut plates may include a bracket and a nut coupleable to the bracket. The nut can receive an externally threaded component (e.g., a bolt or a screw) after the bracket has been secured to the workpiece. When the installed nut plate supports an attached component, a flat face of the bracket can bear against the workpiece to help distribute loads to the workpiece to prevent excessive stresses in the workpiece.
One type of conventional bracket for a nut plate has an expandable one-piece sleeve that a user can insert into an opening of the workpiece. The sleeve is then displaced radially against a tubular surface of the workpiece that defines the workpiece opening. Unfortunately, the one-piece sleeve has a fixed longitudinal length rendering the bracket unsuitable for installation in workpiece openings having longitudinal lengths that are significantly different from the length of the sleeve. A large variety of brackets having sleeves of different dimensions must therefore be kept in stock to install nut plates in different sized openings.
Conventional installation techniques involve expanding the sleeves by swaging the sleeve into the workpiece such that the bracket is fixedly coupled to the structural workpiece. For example, a mandrel moving through a passageway of the sleeve can expand the sleeve to create an interference fit between the sleeve and the workpiece. The installed nut plate bracket resists torques and axial push/pull-out. In addition, the expansion of the sleeve may induce compressive residual stresses into the workpiece material surrounding the opening. If the sleeve extends through a portion of the opening, compressive stresses may be induced only along that portion of the opening. Thus, residual stress may not be induced throughout the length of the opening resulting in a workpiece that is susceptible to fatigue failures.